Re: TCPServer/Socket and Marshal problem

Hello,

On 3 =CE=99=CE=BF=CF=85=CE=BD 2013, at 22:01 , Joel VanderWerf =
<[e-mail]> wrote:

> On 06/03/2013 12:41 PM, Panagiotis Atmatzidis wrote:
>>=20
>> On 3 =CE=99=CE=BF=CF=85=CE=BD 2013, at 21:24 , Joel VanderWerf =
<[e-mail]> wrote:
>>=20
>>> On 06/03/2013 11:47 AM, Panagiotis Atmatzidis wrote:
>>>> Hello,
>>>>=20
>>>> I'm writing a client/server application using TCPSocket and =
TCPServer. To serialize the objects at this point I use Marshal, since =
it comes handy.
>>> ...
>>>> What I notice is that connection ends when the '\n' character =
appears. I think that the issue is me using "@con.gets" method instead =
of something more appropriate. I tried @con.read but since 'read' method =
waits for the remote party to send an 'EOF' or close the connection =
stalls.
>>>>=20
>>>> Is there any other method I can use instead of gets? I did a =
'methods.sort' but I can't see and I don't know how to read about these =
methods using "ri". 'ri TCPSocket::getc' for example doesn't work.
>>>=20
>>> You can try
>>>=20
>>> Marshal.load(conn)
>>>=20
>>> on the client side. The Marshal#load method determines just how many =
bytes to read.
>>=20
>>=20
>> Worked fine! Thank you! I don't get it thought, could you elaborate a =
bit?
>=20
> Sure (sorry to be cryptic!).
>=20
> If you look at the format of marshalled objects, there is always a way =
to determine how many bytes to expect. In the case of fixed length data, =
there is a type field followed by the data (floats for example). In the =
case of strings, arrays, hashes, etc. there are type and length fields =
followed by the items (which themselves will have type and possibly =
length fields). So #load always knows either the number of bytes to read =
or the number of times to iterate to read all the items. Recursively =
build the object tree, and you're done.
>=20
> However, Marshal#load can't know, until this recursion finishes, the =
total number of bytes. There is no length field for the whole serialized =
blob. That's why load(sock.read(n)) doesn't work well with marshal.
>=20
> Btw, if your objects are just strings, numbers, booleans, hashes, and =
arrays, then msgpack is a great alternative to marshal. It's not ruby =
specific, it's fast and compact, and it plays well with non-blocking io.
>=20
> Why non-blocking io? You'll notice that if you Marshal.load(conn) and =
conn takes a long time to send all the bytes, then the thread that =
called #load is blocked. So, just start a thread per connection. That's =
fine if you only need a few connections at a time. With msgpack's =
buffering, it's possible to read only the complete objects from the =
connection, and then the thread is free to go on to another connection =
and read. (See msgpack doc for examples.) Btw, the yajl JSON lib does =
something like this too.
>=20
> Cheers!

Thanks for the amazing explanation!=20

I will try msgpack since my objects are just strings and arrays :-)


Panagiotis (atmosx) Atmatzidis

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